Why are spinewhack-tests not indicitive of lock strength?

[hoxhunbe]

Also, there was a post from a forum member here a few months back about him slipping from a roof and as he slid towards the edge of the roof he stabbed (in reverse grip with edge facing away) his Griptilian into the roof and it held his weight and possibly saved his life.

If knife "X" fails a spinewhack test does that mean it would fail in a situation like the one described above? The difference being an abrupt, jarring strike (spinewhack) versus a (relatively) slower loading of the lock.

The spine whack is as valid in testing lock strength -- or at least one particular aspect of lock strength -- as any other method. Also, in the scenario you describe above, pressure is exerted on the knife is in the opposite direction to that tested by spine whacks. Had this member stabbed the blade, edge inwards, into the roofing as he fell, the knife may have closed on him. That would have certainly changed things. Remember, folding knives are fundamentally stronger when pressed against the edge (and into the stop bar or similar stopping mechanism) than they are when pressure is applied downwards from the spine. Accidents happen, and it's awfully nice to know if your knife -- and your fingers! -- will stand up to an errant blow on the top of your blade.

 

[singularity35]

Just like "they" say that there's nothing to be learned from destruction tests...

 

[kniferbro]

The spine whack is as valid in testing lock strength -- or at least one particular aspect of lock strength -- as any other method. Also, in the scenario you describe above, pressure is exerted on the knife is in the opposite direction to that tested by spine whacks. Had this member stabbed the blade, edge inwards, into the roofing as he fell, the knife may have closed on him. That would have certainly changed things. Remember, folding knives are fundamentally stronger when pressed against the edge (and into the stop bar or similar stopping mechanism) than they are when pressure is applied downwards from the spine. Accidents happen, and it's awfully nice to know if your knife -- and your fingers! -- will stand up to an errant blow on the top of your blade.

Thank you this was the answer I was looking for.

 

[10mm Glock]

Let me preface this post with the statement that I am fully aware that spinewhack tests are NOT a measure of lock strength. I read somewhere (still can't find it) about why spinewhack tests aren't a real test of lock strength, but I forgot the reasons why! Could anyone reeducate me on the subject?o

Also, there was a post from a forum member here a few months back about him slipping from a roof and as he slid towards the edge of the roof he stabbed (in reverse grip with edge facing away) his Griptilian into the roof and it held his weight and possibly saved his life.

If knife "X" fails a spinewhack test does that mean it would fail in a situation like the one described above? The difference being an abrupt, jarring strike (spinewhack) versus a (relatively) slower loading of the lock.

Again, I am FULLY aware about the invalidity of spinewhack tests! I just would like to know why!

I think you're describing a Guy who was sliding off a roof stabbed a knife edge up towards the sky while sliding, thus making it a pressure on the LOCK of the blade incident. Am I wrong? If not it was like a spine "pressure" test. I completely believe a BM grip can handle the force on the lock. But just how hard did he have to stab the roof? Pretty darn hard.

 

[Poez]

.... But just how hard did he have to stab the roof? Pretty darn hard.

Not like he really stabbed the roof: try to stab a plywood and see how much good it does.... I remember the story: he was sliding because that part of the roof turned out to be wet and he was loosing traction. Fast opening and the blade itself in that particular case I guess was more important than the lock strength. Even friction folder would do for the purpose: bad example.

 

[Karda]

There's no reason why the spine whack test is not a valid way to test lock strength. Except in places like bladeforums, where people don't like to see their favorite knives actually put to the test. It makes us look like chumps when our favorite brands by our favorite knifemakers that we spend so much money and adoration over fail.

Spinewhacking is akin to a destruction test, and gives about as much real data as one. Highly subjective and controversial is their only claim to fame. They show more about the mentality of the user than they do about the knife. A folding knife if used properly and for it's intended purpose should hold up as designed quite fine. The problem is most people like to test limits too often and often the result is damage causing failure. Many times it is even user error that some will never admit to.

 

[kreole]

A few years back I was gutting the top floor of a house, cut up something with my Gayle Bradley, and while pulling it back towards my pocket, I hit a beam to my right I didn't notice, smacking the knife on the spine hard. If it had closed, I would have had a nice cut across my fingers.

I don't test my knives that way but see the use in the information. That's the only time I've needed a knife to not fail by spinewhack, but I'm glad it did. Given how rarely useful it is, I would say the results gets hyped up too much.

 

[Goosey]

I don't see why a spinewhack is somehow a stupid or silly test. I don't do it to my knives, but it shows if the knife can or cannot handle a whack to the spine.

I'm confused why some people are hatin' on it, if someone wants a knife that can take a whack on the spine, so be it.

 

[Chris "Anagarika"]

Hanging weight: lock strength test.
Spine whack: shock test. How the spring tension of the lock + surface friction keeping the lock in place & not disengaged by the jarring shock force.

STR has this discussed on his subforum, under tips & tricks sticky

 

[Karda]

I don't see why a spinewhack is somehow a stupid or silly test. I don't do it to my knives, but it shows if the knife can or cannot handle a whack to the spine.

I'm confused why some people are hatin' on it, if someone wants a knife that can take a whack on the spine, so be it.

Because spinewhacking can deform or otherwise ruin a working lock, just as doing things with your knife that they were not designed to do can.
It amounts to abuse and user error.

 

[Goosey]

Because spinewhacking can deform or otherwise ruin a working lock, just as doing things with your knife that they were not designed to do can.
It amounts to abuse and user error.

Yes, well, don't do it with your own knife, let other people do it sometimes there's no time for thinking about correct usage, like when you're sliding off a roof.


Just playing a bit of devil's advocate

 

[Karda]

Yes, well, don't do it with your own knife, let other people do it sometimes there's no time for thinking about correct usage, like when you're sliding off a roof.


Just playing a bit of devil's advocate

If you're sliding off a roof and use your knife to stop you and it fails resulting in your fingers getting cut/chopped....who's fault is it?
Surely not the manufacturers..........
Common sense and forethought should be priorities in any situation.

 

[10mm Glock]

Everytime I reset the lock bar on my HEST 2.0 I spine whack it. I know it's going to pass it anyway. I did have a few customers actually ask for a light spine whack test on Sebenzas before I shipped them out. I never had a Reeve fail a spine whack test ever.

I hated doing it, since it wasn't my knife, but I did it because I know they were going to check it when received so I humored them. My personal Sebbies got full on spine whack tests never failed.

Anyway off to the next thread for me

 

[dsmegst]

In some ways, it's like a crash testing cars. Once you do it hard enough to give you a sense of security, the knife is to some degree damaged. I don't do it on my knives but if someone else does with an identical knife theirs, I secretly feel good about the fact that it "passed."

 

[singularity35]

In some ways, it's like a crash testing cars. Once you do it hard enough to give you a sense of security, the knife is to some degree damaged. I don't do it on my knives but if someone else does with an identical knife theirs, I secretly feel good about the fact that it "passed."

Yep, isn't that how we know that volvos are safe? Doesn't mean you have to crash yours.

 

[kniferbro]

Hanging weight: lock strength test.
Spine whack: shock test. How the spring tension of the lock + surface friction keeping the lock in place & not disengaged by the jarring shock force.

STR has this discussed on his subforum, under tips & tricks sticky

Thank you Chris, I guess my real question was more along the lines of your response. I wanted to know the difference between a "shock" test and a hanging weight test. I should have asked for the physical/mechanical differences exerted on the lock in the two different scenarios.

 

[Ankerson]

Spine tapping is a valid useful test to make sure the lock is within specs and safe.

I would say no harder than this Video here.

[youtube]zKRjaKQbCvo[/youtube]

 

[me2]

The spine whack test is perfectly valid if you expect that your folder might get whacked on the spine. Several users have given examples of that happening during using their knives in tight quarters. Spyderco had a line of knives designed and marketed for Martial Blade Craft, with appropriately stout locks. These should be able to pass a spine whack, since pretty much anything can happen if you're having to use a knife for that purpose. One handed modern folders do not work like slip joints or lock backs with half stops. If the lock lets go, the blade is free to swing. A few taps on the spine will tell the tale. Perhaps standing in a door, and turning around would be a good way to simulate the working scenario where a spine can get some impact. Lock strength (slow load against the spine), reliability (does it fully lock every time), and impact resistance (spine whack) can all be considered and tested by knife owners. None have to be to failure.

 

[gooeytek]

Spine-whack tests are invalid for folding knives, because when you are exerting impact pressure to the spine of the knife, you are obviously using the knife incorrectly. By the nature and premise of a spine-whack test, you are automatically discounting two whole (and popular) categories of folding knives: slipjoints, and friction folders. How about a handle-whack test to determine integrity of handle construction and materials used? How about an edge-whack test? I think that'll be a truer test of how a knife blade should hold up in the real world. Maybe a dirt and mud test to check how well or badly the folding knife still functions after being subjected to debris and grit internally? At no time during real-world use of any of my folding knives would a spine-whack matter.

 

[10mm Glock]

In some ways, it's like a crash testing cars. Once you do it hard enough to give you a sense of security, the knife is to some degree damaged. I don't do it on my knives but if someone else does with an identical knife theirs, I secretly feel good about the fact that it "passed."

The only problem with that is, every knife is slightly different. Just because another identical knife passed it doesn't mean yours will. CRK were the only ones that I found consistent.